<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>DOM对象转成jQuery对象</title>
    <script type="text/javascript" src="./script/jquery-3.6.0.min.js"></script>
    <script type="text/javascript">
        window.onload = function (){
            //演示通过dom对象来获取输入框的value
            //username就是dom对象
            var username = document.getElementById("username");
            alert("username value= " + username.value);

            //通过jquery对象来获取输入框的value
            //把username dom 对象转成 jquery对象
            var $username = $(username);
            //使用jquery的方法来获取value
            alert("$username value= " + $username.val())
        }
    </script>
</head>
<body>
用户名 <input type="text" id="username" name="username" value="韩顺平教育"/>
</body>
</html>